The present invention relates to an endless traction band for a snowmobile and to the sprocket wheel used therewith. Such a traction band is designed to travel on snow, on which the use of wheeled vehicle is of little help.
A traction band is usually made of a reinforced molded rubber material or an assembly of interconnected parts that form an endless band, having longitudinally spaced and transversely disposed stiffeners embedded in the rubber material. The endless band is flexible around a lateral axis so that it can follow the curvature around sprocket and idler wheels. Each traction band is designed to support a significant portion of the total weight of the vehicle and apply a traction force on the ground.
As used herein, the term “rubber” relates to any elastic and primarily non-metallic materials such as rubber, elastomers, or combinations thereof used in the manufacture of endless traction bands.
Among all off-road vehicles equipped with traction bands, recreational snowmobiles are unique in that they are equipped with only one traction band while essentially all other vehicles are equipped with two or more traction bands. Examples of such other vehicles are bulldozers, military tanks, snow-surfacing machines, etc.
Without excluding any other applications, traction bands for vehicles traveling at moderate or high speeds, which are essentially snowmobiles, are the prime interest of the present invention. The snowmobiles are then used in the present description as the main application for the traction bands and the method in accordance with the present invention.
A snowmobile is often equipped with a rubber-band traction band that features an endless body made of a reinforced rubber material with longitudinally spaced and transversely disposed stiffeners embedded in the rubber material. The body typically defines a longitudinally extending central portion and a pair of lateral band portions each of which is located on one of the sides of the central portion. The traction band is positioned under the chassis of the snowmobile and supports most of the weight. A pair of front ski-like runners is provided to steer the snowmobile and support the other portion of the weight.
The body of the traction band has a ground-engaging outer side and an inner side. The inner side cooperates with a suspension system. The weight of the traction band is supported by either a pair of slide rails or a plurality of bogey wheels that are mechanically connected to the other parts of the suspension system. The suspension system is also used to support the traction band with respect to lateral movements.
The ground-engaging outer side has a tread pattern that is repeated uniformly or not over the entire length of the traction band. The tread pattern comprises a plurality of projecting traction lugs that are configured and disposed in accordance with the purpose for which the traction band is designed. The traction lugs are used to increase the adherence of the snowmobile on snow mud, melting snow, ice or any other similar surfaces.
Further, the opposite lateral band portions are usually separated from the central portion by a corresponding row of holes. Each row of holes generally cooperates with the teeth of the corresponding sprocket wheels and idler wheels or simply provides a support area for metal clip.
The ground-engaging outer side usually has a sequence of profiles that is repeated uniformly or not over the total length of the traction band. Each sequence of profiles or tread pattern comprises laterally extending profiles that are longitudinally spaced apart by flat areas. Each profile comprises a series of outwardly projecting traction lugs. The choice of lug profiles that are selected to be part of every sequence of profiles, which is repeated along the circumference of the traction band, has an influence on the band behavior on the snow, on the snowmobile performances and on the comfort of the driver. These criteria are very critical in a marketing point of view, since they differentiate products from one another in the eye of a potential customer.
There is always a need for a traction band which provides better performance and better comfort for the driver.